The writing process for the majority of Metallicaâs albums have followed the same process. A large slew of guitar riffs written primarily by James Hetfield, sometimes Kirk Hammett, and rarely the bandâs bass player, (that now being bass virtuoso Robert Trujillo) are reviewed and selected.
1 Delhi is most polluted city in the world in PM2.5 concentrations. 2  Half of the top 20 most polluted cities were in India, according to data.  PM2.5 is considered most harmful to health.
(CNN) -- Air quality in most cities that monitor their pollution levels exceed what the World Health Organization deems as safe. Delhi has the highest level of the airborne particulate matter, PM2.5 considered most harmful to health, with 153 micrograms. Not far behind is another Indian city, Patna with 149 micrograms.nd the world's most polluted city is... Air pollution has spread by increasing reliance on fossil fuels, coal-fired power plants, cars and the use of biomass for cooking and heating.